Outdoor power equipment includes such devices as mowers, trimmers, edgers, chainsaws, blowers and the like. These devices are often used to perform tasks that inherently require the devices to be mobile. Accordingly, these devices are typically made to be relatively robust and capable of handling difficult work in hostile environments, while balancing the requirement for mobility.
Powering such devices could be accomplished in any number of ways. However, for outdoor power equipment that is intended to be handheld, size and weight become important considerations. Thus, one common source of power for handheld outdoor power equipment has been the internal combustion engine due to its ability to provide ample power in a relatively small package. Internal combustion engines for handheld outdoor power equipment typically employ engines that blend air and fuel in a carburetor. The carburetor is a well known device, and employs an internal venturi to enable airflow provided into the engine to draw fuel into the airstream. In many cases, the flow of air and fuel into the engine can be controlled using a throttle valve.
In some engines, the position of the throttle valve may be adjusted by an operator employing some form of trigger mechanism, usually coupled to the throttle valve via a cable. The trigger mechanism may be provided on a handle of the machine so that it can be operated by a hand or fingers of the operator. In such an engine, when the trigger mechanism is not depressed, the engine is typically enabled to return to an idle condition. However, not all engines are necessarily constructed to employ trigger mechanisms. Some engines employ a series of discrete throttle valve positions that are manually selectable to increase the simplicity of design. In such designs, a lever or selector is typically adjusted manually by the operator to one of the throttle valve positions. Movement between each of these positions therefore requires the operator to manually select a desired position, including the idle position.